#define _CRT_SECURE_NO_WARNINGS 1

#include<iostream>
#include<vector>

using namespace std;

int main()
{
	int n = 0;
	cin >> n;
	vector<int> dp(n+1);
	vector<int> cost(n+1);
	for (int i = 0; i < n; i++)
	{
		cin >> cost[i];
	}
	for (int i = 2; i <= n; i++)
	{
		dp[i] = min(dp[i - 1] + cost[i - 1], dp[i - 2] + cost[i - 2]);
	}


	cout << dp[n] << endl;

	return 0;
}